1. Field of the Invention
The present invention relates to a gear-shaping grindstone which is rotated in mesh with a gear to be ground, thereby to grind and finish the tooth flank, and to a method of fabricating the grindstone.
2. Description of the Related Art
The transmission gear of automobiles and other gears are conventionally ground to high accuracy to reduce noise. A method of grinding these gears consists in rotating a gear-shaped grindstone in mesh with a gear to be ground (hereinafter referred to as the work gear) and grinding the tooth flank of the work gear.
An example of such a grindstone is disclosed in Japanese Unexamined Patent Publication No. 7-108484. The grindstone disclosed in this publication is so configured that a grinding face is formed by fixedly attaching a single layer of a super-abrasive to the toothed portion of a base metal by electrodeposition and an adjustable grinding portion is formed at a predetermined portion on the top land side of the tooth flank by grinding or lapping.
As described in the publication cited above, the conventional grindstone of the above-mentioned type is generally fabricated by fixedly attaching the super-abrasive to the base metal by electrodeposition. In forming a super-abrasive layer by electrodeposition, however, the accuracy of form of the grindstone is dependent on that of the base metal. In order to improve the accuracy of form of the grindstone, the super-abrasive layer is required to be ground or lapped, which in turn requires a special grinding machine or a special lapping machine capable of shaping the teeth.
Also, in view of the fact that the distribution, size, direction and the interval of the super-abrasives of the super-abrasive layer formed by electrodeposition are uncontrollable, the super-abrasive layer is formed unevenly on the tooth flank. As a result, the roughness of the tooth flank of the work gear ground with such a super-abrasive layer is not very satisfactory for a deteriorated accuracy of form.
Further, the electrodeposition is generally used to form a single layer of super-abrasive. Once the grindstone is used until the grinding efficiency is reduced, therefore, it is not an easy matter to restore the particular grindstone into a usable state. Specifically, the entire super-abrasive layer must be removed from the base metal and a new super-abrasive layer formed by electrodeposition again. This job is very bothersome.